The 69-year-old feels that the Fiorentina striker should have been given more time to recover from the injuries which ruined his first season in Italy's Serie A
The Fiorentina striker has struggled with injury throughout the season and did not make his country's preliminary panel for this summer's World Cup.
Heynckes dropped Gomez during his time in charge at the Allianz Arena but feels Low could come to regret his decision to omit the 28-year-old, who has netted 25 times in 59 international appearances.
"Gomez has been injured for a long time," the ex-Bayern boss is quoted as saying by Bild.
"One can understand the decision, but I certainly would have waited until the last moment to see whether Mario got fit again or not.
"The coach has called up Sami Khedira and Miroslav Klose, who were both injured for a long time."
Germany's next World Cup warm-up game is against Cameroon on June 1.